Apparatus for reducing greenhouse gas emission in vessel and vessel including the same

ABSTRACT

The present invention relates to an apparatus for reducing greenhouse gas emission in a vessel and a vessel including the same, in which CO 2  absorbed by taking only a part of the absorbent liquid used when collecting CO 2  is removed, so that the device sizes of an absorbent liquid recycling unit and an absorbent liquid circulating unit is kept small and continuous operation is enabled. Or in which exhaust gas is cooled by a heat exchange method, thereby preventing the decrease in a concentration of an absorbent liquid, and CO 2  absorbed by taking only a part of the absorbent liquid used when collecting CO 2  is removed and an unreacted absorbent liquid is continuously circulated, thereby enabling continuous operation.

TECHNICAL FIELD

The present invention relates to an apparatus for reducing greenhousegas emission in a vessel and a vessel including the same, in which CO₂absorbed by taking only a part of the absorbent liquid used whencollecting CO₂ is removed, so that the device sizes of an absorbentliquid recycling unit and an absorbent liquid circulating unit is keptsmall and continuous operation is enabled.

In addition, the present invention relates to an apparatus for reducinggreenhouse gas emission in a vessel and a vessel including the same, inwhich exhaust gas is cooled by a heat exchange method, therebypreventing the decrease in a concentration of an absorbent liquid, andCO₂ absorbed by taking only a part of the absorbent liquid used whencollecting CO₂ is removed and an unreacted absorbent liquid iscontinuously circulated, thereby enabling continuous operation.

BACKGROUND ART

Recently, global warming and related environmental disasters haveoccurred due to the influence of greenhouse gas emission caused byindiscriminate use of fossil fuels.

In this regard, a series of technologies related to capture and storageof carbon dioxide, which is the representative greenhouse gas, withoutcarbon dioxide emission are called carbon dioxide capture and storage(CCS) technologies. In recent years, CCS technologies have attractedmuch attention. Among CCS technologies, chemical absorption is the mostcommercialized technology in terms of enabling large-scale treatment.

In addition, carbon dioxide emission is regulated through the IMO'sEEDI. The IMO is targeting a reduction of 50% or more in emissions by2050 compared to 2008 and a reduction of 40% in emissions by 2030compared to 2008. Therefore, technologies that do not emit CO₂ orcapture emitted CO₂ are attracting attention.

For reference, among the carbon dioxide capture and storage (CCS)technologies for directly capturing and storing carbon dioxide, a CO₂capture technology may be approached in various ways according to CO₂generation conditions of target processes. Current representativetechnologies are an absorption method, an adsorption method, and amembrane separation method. Among them, the wet absorption method hashigh technological maturity in onshore plants and may easily process CO₂in large quantities. Therefore, the wet absorption method may be said tobe the closest capture technology to commercialization of CCStechnology. As an absorbent agent, amines and ammonia are mainly used.

On the other hand, the above-described technologies for reducing carbondioxide emission or capturing generated carbon dioxide are not currentlycommercialized in vessels, and methods of using hydrogen or ammonia asfuel are currently under development and have not reached the level ofcommercialization.

Furthermore, the need is raised to apply, to vessels, a technology forabsorbing CO₂, which is greenhouse gas among exhaust gases emitted froma vessel engine, with an absorbent liquid, converting CO₂ into materialsthat do not affect environments, discharging the materials, orconverting CO₂ into useful materials and storing the useful materials,and preventing the decrease in absorption performance due to reductionin absorbent liquid caused by exhaust gas emission during operation andconcentration change in absorbent liquid caused by other consumptions.

Moreover, the need is raised to apply, to vessels using LNG or lowsulpur fuel oil as fuel so as to emit a small amount of SO_(x) orprevent SO_(x) emission, a technology for absorbing CO₂, which isgreenhouse gas among exhaust gases emitted from a vessel engine, with anabsorbent liquid, converting CO₂ into materials that do not affectenvironments, discharging the materials, or converting CO₂ into usefulmaterials and storing the useful materials, and preventing the decreasein absorption performance due to reduction in absorbent liquid caused byexhaust gas emission during operation and concentration change inabsorbent liquid caused by other consumptions.

DISCLOSURE Technical Problem

An object of the present invention provides an apparatus for reducinggreenhouse gas emission in a vessel and a vessel including the same, inwhich CO₂ absorbed by taking only a part of the absorbent liquid usedwhen collecting CO₂ is removed, so that the device sizes of an absorbentliquid recycling unit and an absorbent liquid circulating unit is keptsmall and continuous operation is enabled.

Also, an object of the present invention provides an apparatus forreducing greenhouse gas emission in a vessel and a vessel including thesame, in which exhaust gas is cooled by a heat exchange method, therebypreventing the decrease in a concentration of an absorbent liquid, andCO₂ absorbed by taking only a part of the absorbent liquid used whencollecting CO₂ is removed and an unreacted absorbent liquid iscontinuously circulated, thereby enabling continuous operation.

Technical Solution

In order to achieve the above object, the present invention provides anapparatus for reducing greenhouse gas emission in a vessel, theapparatus including: a seawater supply unit that supplies seawater; anabsorbent liquid producing unit that produces and supplies ahigh-concentration CO₂ absorbent liquid; an absorption tower including aCO₂ removing unit that cools exhaust gas discharged from a vessel engineby reacting the exhaust gas with the seawater supplied from the seawatersupply unit, and removes CO₂ by reacting the cooled exhaust gas with theabsorbent liquid supplied from the absorbent liquid producing unit toconvert CO₂ into an aqueous ammonium salt solution; an absorbent liquidrecycling unit that recycles the absorbent liquid and NH₃ by reactingthe aqueous ammonium salt solution discharged from the absorption towerwith an aqueous divalent metal hydroxide solution and circulates andsupplies the absorbent liquid and the NH₃ to the absorption tower forreuse as the absorbent liquid; and an absorbent liquid circulating unitthat circulates the aqueous ammonium salt solution or a part of anunreacted absorbent liquid discharged from a lower end of the absorptiontower through an absorbent liquid circulation line to an upper end ofthe absorption tower.

In addition, the absorbent liquid circulating unit may include: anammonia water circulation pump that circulates the aqueous ammonium saltsolution and a part of the unreacted absorbent liquid through theabsorbent liquid circulation line; and a pH sensor that measures aconcentration of the absorbent liquid supplied to the upper end of theabsorption tower.

The absorbent liquid recycling unit may include: a storage tank thatstores the aqueous divalent metal hydroxide solution; a mixing tank inwhich the aqueous divalent metal hydroxide solution and the aqueousammonium salt solution discharged from the absorption tower are stirredby an agitator to generate NH₃(g) and carbonate; and a filter thatsuctions a solution and precipitate from the mixing tank and separatesthe carbonate.

In addition, the NH₃(g) generated by the mixing tank may be supplied tothe absorption tower, or the absorbent liquid separated by the filtermay be supplied to the absorbent liquid circulating unit.

In addition, the aqueous divalent metal hydroxide solution stored in thestorage tank may be Ca(OH)₂ or Mg(OH)₂ produced by reacting fresh waterwith CaO or MgO.

In addition, fresh water or ammonia water separated by the filter may besupplied to the absorbent liquid producing unit, or surplus fresh wateradditionally generated by the mixing tank relative to a totalcirculating fresh water may be stored in a fresh water tank and reusedwhen the aqueous divalent metal hydroxide solution is generated in thestorage tank.

In addition, the absorption tower may further include a SO_(x) absorbingunit that dissolves and removes SO_(x) while cooling the exhaust gasdischarged from the vessel engine by reacting the exhaust gas with theseawater supplied from the seawater supply unit, and the CO₂ removingunit may cool the exhaust gas, from which the SO_(x) has been removed,by reacting the exhaust gas with the seawater supplied from the seawatersupply unit and may remove CO₂ by reacting the cooled exhaust gas withthe absorbent liquid supplied from the absorbent liquid producing unitto convert CO₂ into the aqueous ammonium salt solution.

In addition, the absorption tower may further include a NO_(x) absorbingunit that absorbs and removes NO_(x) from the exhaust gas emitted fromthe vessel engine, and the CO₂ removing unit may cool the exhaust gas,from which the NO_(x) has been removed, by reacting the exhaust gas withthe seawater supplied from the seawater supply unit and may remove CO₂by reacting the cooled exhaust gas with the absorbent liquid suppliedfrom the absorbent liquid producing unit to convert CO₂ into the aqueousammonium salt solution.

In addition, in the absorption tower, a NO_(x) absorbing unit thatabsorbs and removes NO_(x) from the exhaust gas discharged from thevessel engine, a SO_(x) absorbing unit that dissolves and removes SO_(x)while cooling the exhaust gas, from which the NO_(x) has been removed,through reaction with the seawater supplied from the seawater supplyunit, and the CO₂ removing unit that removes CO₂ by reacting the exhaustgas, from which the SO_(x) has been removed, with the absorbent liquidsupplied from the absorbent liquid producing unit to convert CO₂ intothe aqueous ammonium salt solution may be sequentially stacked.

In addition, the NH₃ recycled by the absorbent liquid recycling unit maybe supplied to the NO_(x) absorbing unit, and the NO_(x) absorbing unitmay absorb the NO_(x) with the NH₃ or may absorb the NO_(x) using ureawater.

In addition, the seawater supply unit may include: a seawater pump thatreceives seawater from the outside of the vessel through a sea chest andpumps the seawater to the SO_(x) absorbing unit; and a seawater controlvalve that controls a spray amount of the seawater supplied from theseawater pump to the SO_(x) absorbing unit according to an amount of theexhaust gas.

The absorbent liquid producing unit may include: a fresh water tank thatstores fresh water; a fresh water control valve that supplies the freshwater from the fresh water tank; a NH₃ storage that stores high-pressureNH₃; an ammonia water tank that produces and stores high-concentrationammonia water, which is the absorbent liquid, by spraying the NH₃supplied from the NH₃ storage to the fresh water supplied by the freshwater control valve; a pH sensor that measures a concentration of theammonia water in the ammonia water tank; and an ammonia water supplypump that supplies the ammonia water from the ammonia water tank to theabsorbent liquid circulating unit.

In addition, the SO_(x) absorbing unit may include: a multi-stageseawater spray nozzle that sprays the seawater supplied from theseawater supply unit downward; and a partition wall-shaped exhaust gasinlet pipe that prevents cleaning water from flowing back, or anumbrella-shaped blocking plate that covers the exhaust gas inlet pipe.

In addition, porous upper plates having a passage through which theexhaust gas passes may be respectively formed in multi-stages under theseawater spray nozzle, so that the seawater and the exhaust gas comeinto contact with each other.

In addition, an absorption apparatus filled with a packing material forallowing the seawater and the exhaust gas to come into contact with eachother may be formed under the seawater spray nozzle, so that theseawater dissolves the SO_(x).

In addition, the CO₂ removing unit may include: an ammonia water spraynozzle that sprays the absorbent liquid downward; a packing materialthat contacts the CO₂ with the ammonia water, which is the absorbentliquid, to convert CO₂ into NH₄HCO₃(aq); a cooling jacket that is formedin multi-stages for each section of an absorption apparatus filled withthe packing material and cools heat generated by a CO₂ absorptionreaction; a water spray that collects NH₃ discharged to the outsidewithout reacting with CO₂; a mist removal plate that is formed in acurved multi-plate shape and returns the ammonia water toward thepacking material; a partition wall that is formed so that the ammoniawater does not flow back; and an umbrella-shaped blocking plate thatcovers an exhaust gas inlet hole surrounded by the partition wall.

In addition, the packing material may include multi-stage distillingcolumn packings designed to increase a contact area per unit volume, anda solution redistributor may be formed between the multi-stagedistilling column packings.

In addition, the absorption tower may further include an exhaust gaseconomizer (EGE) that is formed between the NO_(x) absorbing unit andthe SO_(x) absorbing unit and performs heat exchange between waste heatof the vessel engine and boiler water.

In addition, the apparatus may further include a discharge unitincluding: a cleaning water tank that stores cleaning water dischargedfrom the absorption tower; a water treatment device including afiltering unit that controls turbidity to satisfy an outboard dischargecondition of the cleaning water transferred to the cleaning water tankby a transfer pump, and a neutralizing agent injecting unit thatcontrols pH; and a sludge storage tank that separates and stores solidemissions.

On the other hand, the present invention may provide a vessel includingthe above-described apparatus.

In order to achieve another object, the present invention provides anapparatus for reducing greenhouse gas emission in a vessel, theapparatus including: an exhaust gas cooling unit that cools exhaust gasdischarged from a vessel engine; an absorbent liquid producing unit thatproduces and supplies a high-concentration CO₂ absorbent liquid; anabsorption tower including a CO₂ removing unit that removes CO₂ byreacting the exhaust gas cooled by the exhaust gas cooling unit with theabsorbent liquid supplied from the absorbent liquid producing unit toconvert CO₂ into an aqueous ammonium salt solution; an absorbent liquidrecycling unit that recycles the absorbent liquid and NH₃ by reactingthe aqueous ammonium salt solution discharged from the absorption towerwith an aqueous divalent metal hydroxide solution and circulates andsupplies the absorbent liquid and the NH₃ to the absorption tower forreuse as the absorbent liquid; and an absorbent liquid circulating unitthat circulates the aqueous ammonium salt solution or a part of anunreacted absorbent liquid discharged from a lower end of the absorptiontower through an absorbent liquid circulation line to an upper end ofthe absorption tower.

In addition, the absorbent liquid circulating unit may include: anammonia water circulation pump that circulates the aqueous ammonium saltsolution and a part of the unreacted absorbent liquid through theabsorbent liquid circulation line; and a pH sensor that measures aconcentration of the absorbent liquid supplied to the upper end of theabsorption tower.

The absorbent liquid recycling unit may include: a storage tank thatstores the aqueous divalent metal hydroxide solution; a mixing tank inwhich the aqueous divalent metal hydroxide solution and the aqueousammonium salt solution discharged from the absorption tower are stirredby an agitator to generate NH₃(g) and carbonate; and a filter thatsuctions a solution and precipitate from the mixing tank and separatesthe carbonate.

The NH₃(g) generated by the mixing tank may be supplied to theabsorption tower, or the absorbent liquid separated by the filter may besupplied to the absorbent liquid circulating unit.

The aqueous divalent metal hydroxide solution stored in the storage tankmay be Ca(OH)₂ or Mg(OH)₂ produced by reacting fresh water with CaO orMgO.

Fresh water or ammonia water separated by the filter may be supplied tothe absorbent liquid producing unit, or surplus fresh water additionallygenerated by the mixing tank relative to a total circulating fresh watermay be stored in a fresh water tank and reused when the aqueous divalentmetal hydroxide solution is generated in the storage tank.

The vessel engine may use liquefied natural gas (LNG) or low sulphurmarine gas oil (LSMGO) as fuel.

The exhaust gas cooling unit may cool the exhaust gas to a temperatureof 27° C. to 33° C. by circulating fresh water supplied from an onboardcooling system through a heat exchange pipe surrounding an exhaust gasdischarge pipe.

The absorption tower may further include a NO_(x) absorbing unit thatabsorbs and removes NO_(x) from the exhaust gas emitted from the vesselengine, and the CO₂ removing unit may remove CO₂ by reacting the exhaustgas, from which the NO_(x) has been removed and which is cooled by theexhaust gas cooling unit, with the absorbent liquid supplied from theabsorbent liquid producing unit to convert CO₂ into the aqueous ammoniumsalt solution.

In addition, the NO_(x) absorbing unit and the CO₂ removing unit may bestacked.

In addition, the NH₃ recycled by the absorbent liquid recycling unit maybe supplied to the NO_(x) absorbing unit, and the NO_(x) absorbing unitmay absorb the NO_(x) with the NH₃ or absorbs the NO_(x) using ureawater.

In addition, the absorbent liquid producing unit may include: a freshwater tank that stores fresh water; a fresh water control valve thatsupplies the fresh water from the fresh water tank; a NH₃ storage thatstores high-pressure NH₃; an ammonia water tank that produces and storeshigh-concentration ammonia water, which is the absorbent liquid, byspraying the NH₃ supplied from the NH₃ storage to the fresh watersupplied by the fresh water control valve; a pH sensor that measures aconcentration of the ammonia water in the ammonia water tank; and anammonia water supply pump that supplies the ammonia water from theammonia water tank to the absorbent liquid circulating unit.

In addition, the CO₂ removing unit may include: an ammonia water spraynozzle that sprays the absorbent liquid downward; a packing materialthat contacts the CO₂ with the ammonia water, which is the absorbentliquid, to convert the CO₂ into NH₄HCO₃(aq); a cooling jacket that isformed in multi-stages for each section of an absorption apparatusfilled with the packing material and cools heat generated by a CO₂absorption reaction; a water spray that collects NH₃ discharged to theoutside without reacting with CO₂; a mist removal plate that is formedin a curved multi-plate shape and returns the ammonia water toward thepacking material; a partition wall that is formed so that the ammoniawater does not leak out; and an umbrella-shaped blocking plate thatcovers an exhaust gas inlet hole surrounded by the partition wall.

In addition, the packing material may include multi-stage distillingcolumn packings designed to increase a contact area per unit volume, anda solution redistributor may be formed between the multi-stagedistilling column packings.

In addition, the absorption tower may further include an exhaust gaseconomizer (EGE) that is formed between the NO_(x) absorbing unit andthe CO₂ removing unit and performs heat exchange between waste heat ofthe vessel engine and boiler water.

On the other hand, the present invention may provide a vessel includingthe above-described apparatus.

Advantageous Effects

According to the present invention, since CO₂ absorbed by taking only apart of the absorbent liquid used when collecting CO₂ is removed, thedevice sizes of an absorbent liquid recycling unit and an absorbentliquid circulating unit may be kept small and continuous operation maybe enabled.

In addition, it is possible to flexibly cope with a CO₂ absorption rateaccording to a load change of a vessel engine. A high-concentrationabsorbent liquid may be supplied to prevent the decrease in greenhousegas absorption performance. A pressurization system may be applied toprevent the loss of absorbent liquid due to the natural evaporation ofhigh-concentration absorbent liquid.

Furthermore, in order to satisfy the IMO greenhouse gas emissionregulations, greenhouse gas may be converted into materials that do notaffect environments and then separately discharged or may be convertedinto useful materials and then stored. NH₃ may be recycled to minimizeconsumption of relatively expensive NH₃. A capacity size of a rear endof a filter may be reduced. Side reactions caused by SO_(x) remainingduring NH₃ recycling may be removed, thereby minimizing the loss of NH₃and preventing impurities from being included when recovering ammonia.

In addition, according to the present invention exhaust gas is cooled bya heat exchange method, thereby preventing the decrease in aconcentration of an absorbent liquid. Since CO₂ absorbed by taking onlya part of the absorbent liquid used when collecting CO₂ is removed, thedevice sizes of an absorbent liquid recycling unit and an absorbentliquid circulating unit may be kept small and continuous operation maybe enabled.

In addition, it is possible to flexibly cope with a CO₂ absorption rateaccording to a load change of a vessel engine. A high-concentrationabsorbent liquid may be supplied to prevent the decrease in greenhousegas absorption performance. A pressurization system may be applied toprevent the loss of absorbent liquid due to the natural evaporation ofhigh-concentration absorbent liquid.

Moreover, in order to satisfy the IMO greenhouse gas emissionregulations, greenhouse gas may be converted into materials that do notaffect environments and then separately discharged or may be convertedinto useful materials and then stored. NH₃ may be recycled to minimizeconsumption of relatively expensive NH₃. A capacity size of a rear endof a filter may be reduced. Greenhouse gases may be stored in the formof carbonates that exist in the natural state, and may be discharged tothe sea. Side reactions caused by NO_(x) or SO_(x) remaining during NH₃recycling may be removed, thereby minimizing the loss of NH₃ andpreventing impurities from being included when recovering ammonia.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of an apparatus for reducinggreenhouse gas emission in a vessel, according to an embodiment of thepresent invention.

FIG. 2 is a circuit diagram of a system implementing the apparatus forreducing greenhouse gas emission in a vessel, illustrated in FIG. 1 .

FIG. 3 separately illustrates a seawater supply unit of the apparatusfor reducing greenhouse gas emission in a vessel, illustrated in FIG. 2.

FIG. 4 separately illustrates an absorbent liquid producing unit, anabsorbent liquid recycling unit, and an absorbent liquid circulatingunit of the apparatus for reducing greenhouse gas emission in a vessel,illustrated in FIG. 2 .

FIG. 5 separately illustrates an absorption tower of the apparatus forreducing greenhouse gas emission in a vessel, illustrated in FIG. 2 .

FIG. 6 separately illustrates a SO_(x) absorbing unit of the absorptiontower of FIG. 5 .

FIG. 7 separately illustrates a steam generating unit and a dischargeunit of the apparatus for reducing greenhouse gas emission in a vessel,illustrated in FIG. 2 .

FIG. 8 illustrates various packing materials applied to the apparatusfor reducing greenhouse gas emission in a vessel, illustrated in FIG. 2.

FIG. 9 illustrates an ammonia water spray nozzle applied to theapparatus for reducing greenhouse gas emission in a vessel, illustratedin FIG. 2 .

FIG. 10 is a schematic configuration diagram of an apparatus forreducing greenhouse gas emission in a vessel, according to anotherembodiment of the present invention.

FIG. 11 is a circuit diagram of a system implementing the apparatus forreducing greenhouse gas emission in a vessel according to anotherembodiment, illustrated in FIG. 10 .

FIG. 12 separately illustrates an exhaust gas cooling unit and anabsorption tower of the apparatus for reducing greenhouse gas emissionin a vessel according to another embodiment, illustrated in FIG. 11 .

FIG. 13 separately illustrates an absorbent liquid producing unit, anabsorbent liquid recycling unit, and an absorbent liquid circulatingunit of the apparatus for reducing greenhouse gas emission in a vesselaccording to another embodiment, illustrated in FIG. 11 .

FIG. 14 separately illustrates a steam generating unit of the apparatusfor reducing greenhouse gas emission in a vessel according to anotherembodiment, illustrated in FIG. 11 .

FIG. 15 illustrates various packing materials applied to the apparatusfor reducing greenhouse gas emission in a vessel according to anotherembodiment, illustrated in FIG. 11 .

FIG. 16 illustrates an ammonia water spray nozzle applied to theapparatus for reducing greenhouse gas emission in a vessel according toanother embodiment, illustrated in FIG. 11 .

BEST MODE

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings so that the presentinvention can be easily carried out by those of ordinary skill in theart. The present invention may be embodied in many different forms andis not limited to embodiments of the present invention described herein.

Referring to FIG. 1 , an apparatus for reducing greenhouse gas emissionin a vessel according to an embodiment of the present inventionincludes: a seawater supply unit 110 that supplies seawater; anabsorbent liquid producing unit 120 that produces and supplies ahigh-concentration CO₂ absorbent liquid; an absorption tower 130including a CO₂ removing unit 131 that cools exhaust gas discharged froma vessel engine 10 by reacting the exhaust gas with the seawatersupplied from the seawater supply unit 110, and removes CO₂ by reactingthe cooled exhaust gas with the absorbent liquid supplied from theabsorbent liquid producing unit 120 to convert CO₂ into an aqueousammonium salt solution; an absorbent liquid recycling unit 140 thatrecycles an absorbent liquid and NH₃ by reacting the aqueous ammoniumsalt solution discharged from the absorption tower 130 with an aqueousdivalent metal hydroxide solution and circulates and supplies theabsorbent liquid and the NH₃ to the absorption tower 130 for reuse asthe absorbent liquid; and an absorbent liquid circulating unit 150 thatcirculates the aqueous ammonium salt solution or a part of an unreactedabsorbent liquid discharged from a lower end of the absorption tower 130through an absorbent liquid circulation line A to an upper end of theabsorption tower 130. Only a part of the aqueous ammonium salt solutionis converted into carbonate and the remaining unreacted absorbent liquidis circulated to the absorption tower 130, thereby maintaining a CO₂absorption rate.

Here, according to the type and specification of the vessel engine(low-pressure engine or high-pressure engine) used in a main engine orpower generation engine and the type of fuel supplied to the vesselengine (HFO, MDO, LNG, MGO, LSMGO, ammonia, etc.), the absorption tower130 may optionally include, in addition to the CO₂ removing unit, aNO_(x) absorbing unit that removes nitrogen oxide or a SO_(x) absorbingunit, or may include both the NO_(x) absorbing unit and the SO_(x)absorbing unit.

In particular, when low sulphur marine gas oil (LSMGO) is used as thefuel of the vessel engine, a SO_(x) absorbing unit capable ofsimultaneously performing cooling of exhaust gas and absorption andremoval by dissolution of SO_(x) may be additionally provided.

Hereinafter, an embodiment in which the NO_(x) absorbing unit, theSO_(x) absorbing unit, and the CO₂ removing unit are sequentiallystacked on the absorption tower 130 will be described, but the presentinvention is not limited thereto. As described above, the NO_(x)absorbing unit and/or the SO_(x) absorbing unit may or may not beoptionally included according to the vessel engine specification and thefuel type.

Hereinafter, the apparatus for reducing greenhouse gas emission in thevessel will be described in detail with reference to FIGS. 1 to 9 .

First, a seawater supply unit 110 supplies seawater to an absorptiontower 130 so that temperature of high-temperature and high-pressureexhaust gas is lowered to facilitate absorption of CO₂ by an absorbentliquid.

Specifically, as illustrated in FIGS. 2 and 3 , the seawater supply unit110 may include: a seawater pump 111 that suctions seawater from theoutside of the vessel through a sea chest (not illustrated) and pumpsthe seawater to a SO_(x) absorbing unit 132 of the absorption tower 130;and a seawater control valve 112 that controls the spray amount of theseawater supplied to the SO_(x) absorbing unit 132 according to theamount of exhaust gas. Here, the seawater pump 111 may separatelyinclude a suction pump that suctions the seawater from the outside ofthe vessel and a seawater transfer pump that pumps and transfers theseawater to the SO_(x) absorbing unit 132.

For reference, when the vessel is berthing or sailing, seawater may beselectively supplied to the seawater pump 111 from a high sea chest thatsuctions upper seawater or a low sea chest that suctions lower seawateraccording to the depth of water. That is, when the vessel is berthing,the high sea chest may be used because the upper seawater is cleanerthan the lower seawater, and when the vessel is sailing, the low seachest may be used because the lower seawater is cleaner than the upperseawater.

Here, the seawater control valve 112 may be a manually operateddiaphragm valve or a solenoid type valve that controls the flow rate ofseawater, but the present invention is not limited thereto. Any type ofvalve may be applied as long as the amount of seawater sprayed through aseawater spray nozzle 132 a of the SO_(x) absorbing unit 132 can becontrolled according to the amount of exhaust gas.

Next, in order to supply a high-concentration absorbent liquid formaintaining the concentration of the absorbent liquid, the absorbentliquid producing unit 120 reacts fresh water with NH₃ as shown in[Chemical Formula 1] below to produce high-concentration ammonia water(NH₄OH(aq)), which is a high-concentration CO₂ absorbent liquid, andsupplies the high-concentration ammonia water (NH₄OH(aq)) through theabsorbent liquid circulating unit 150 to the CO₂ removing unit 131formed at the upper end of the absorption tower 130.

NH₃+H₂O->NH₄OH(aq), (exothermic reaction 1650 MJ/ton)   [ChemicalFormula 1]

Specifically, as illustrated in FIGS. 2 and 4 , the absorbent liquidproducing unit 120 may include: a fresh water tank (not illustrated)that stores fresh water; a fresh water control valve 121 that suppliesthe fresh water from the fresh water tank to an ammonia water tank 123;a NH₃ storage 122 that stores high-pressure NH₃; the ammonia water tank123 that produces and stores high-concentration ammonia water byspraying NH₃ supplied from the NH₃ storage 122 to the fresh watersupplied by the fresh water control valve 121; a pH sensor 124 thatmeasures a concentration of the ammonia water in the ammonia water tank123; and an ammonia water supply pump 125 that supplies thehigh-concentration ammonia water from the ammonia water tank 123 to anabsorbent liquid circulation line A of the absorbent liquid circulatingunit 150.

The concentration of the ammonia water that is the absorbent liquidcirculating through the absorption tower 130 and the absorbent liquidrecycling unit 140 along the absorbent liquid circulation line A changesas the operation is repeated. For example, the concentration of theammonia water is reduced when NH₃ is supplied to the NO_(x) absorbingunit 133 and used to absorb and remove NO_(x), or when NH₃ passesthrough the absorption tower 130 and is exhausted to the atmospheretogether with the exhaust gas. When the concentration of the ammoniawater is reduced, the absorbent liquid producing unit 120 supplies thehigh-concentration ammonia water to the absorbent liquid circulationline A of the absorbent liquid circulating unit 150 to compensate forthe reduced concentration of the ammonia water so that the ammonia wateris constantly maintained at a designed concentration.

On the other hand, since the high-concentration ammonia water has ahigher partial pressure of NH₃(g) than that of the low-concentrationammonia water at the same temperature, NH₃ is relatively more evaporatedin an atmospheric pressure state, resulting in an increase in loss.Therefore, in order to store the high-concentration ammonia water, it isnecessary to lower temperature in order for increasing the solubilityand reducing the vapor pressure of NH₃(g) and to operate under apressurization system.

That is, in order to prevent a phenomenon that NH₃(g) is evaporated andlost to the atmosphere, compressed air of a constant pressure may beinjected into the ammonia water tank 123 so that the pressure in theammonia water tank 123 is maintained to be high, thereby effectivelypreventing the evaporation loss of NH₃.

For example, since NH₃ may be stored in a liquid state at −34° C. and8.5 bar, 50% concentration of ammonia water may be stored in the ammoniawater tank 123 by maintaining the inside of the ammonia water tank 123at a constant pressure by using compressed air of 7 bar available in thevessel.

In addition, a safety valve 123 a for preventing overpressure of theammonia water tank 123 may be installed.

Next, the absorption tower 130 includes a CO₂ removing unit 131 thatcools exhaust gas discharged from the vessel engine 10 by reacting theexhaust gas with the seawater supplied from the seawater supply unit110, reacts CO₂ of the cooled exhaust gas with ammonia water suppliedfrom the absorbent liquid producing unit 120 or ammonia watercirculating through the absorbent liquid circulation line A, andconverts CO₂ into a high-concentration aqueous ammonium salt solution(NH₄HCO₃(aq)) to remove CO₂ as shown in [Chemical Formula 2] below.

2NH₄OH+CO₂->(NH₄)₂CO₃+H₂O

(NH₄)₂CO₃+CO₂+H₂O->2NH₄HCO₃   [Chemical Formula 2]

Specifically, as illustrated in FIG. 3 , the CO₂ removing unit 131 mayinclude: an ammonia water spray nozzle 131 a that sprays the ammoniawater supplied from the absorbent liquid circulating unit 150 downward;a packing material 131 b that contacts CO₂ of the exhaust gas with theammonia water and converts CO₂ into high-concentration NH₄HCO₃(aq); acooling jacket (not illustrated) that is formed in multi-stages for eachsection of an absorption apparatus filled with the packing material 131b and cools heat generated by the CO₂ absorption reaction; a water spray131 c that collects NH₃ discharged to the atmosphere without reactingwith CO₂; a mist removal plate 131 d that is formed in a curvedmulti-plate shape and returns the ammonia water scattered when sprayedby the ammonia water spray nozzle 131 a toward the packing material 131b; a partition wall 131 e that is formed so that the ammonia waterpassing through the packing material 131 b does not flow back to theSO_(x) absorbing unit 132; and an umbrella-shaped blocking plate 131 fthat covers an exhaust gas inlet hole surrounded by the partition wall131 e.

Here, the cooling jacket may cool heat to 30° C. to 50° C. at which thematerial transfer is smoothest, so that NH₃ is not evaporated and lostwhile maintaining a CO₂ absorption rate at a certain level.

On the other hand, the CO₂ removing unit 131 may be considered invarious forms so as to operate within an allowable pressure drop of anexhaust pipe required by an engine specification while increasing acontact area between the exhaust gas and NH₃. For example, the packingmaterial 131 b may include multi-stage distilling column packingsdesigned to increase a contact area per unit volume. As illustrated inFIG. 8 , a distilling column packing suitable for an absorption processmay be selected considering the contact area per unit area, the pressuredrop of gas, and the flooding velocity. As illustrated in FIG. 9 , theammonia water spray nozzle 131 a may be provided in a ladder pipe formFIG. 9A or a spray form FIG. 9B.

In addition, a solution redistributor (not illustrated) may be formedbetween the distilling column packings so as to prevent channeling whenthe ammonia water passes downward through the packing material 131 b,the exhaust gas passes upward through the packing material 131 b, andthe ammonia water and the exhaust gas contact each other.

In addition, the mist removal plate 131 d allows the scattered ammoniawater to adhere to the curved multi-plate, so that droplets becomelarge, and drains the ammonia water toward the packing material 131 b bythe own weight thereof.

On the other hand, when the vessel engine 10 uses LNG as fuel, SO_(x)may not be generated, but when the vessel engine 10 uses LSMGO as fuel,the absorption tower 130 may further include the SO_(x) absorbing unit132.

That is, the SO_(x) absorbing unit 132 may dissolve and remove SO_(x)while cooling the exhaust gas discharged from the vessel engine 10 byreacting the exhaust gas with the seawater supplied from the seawatersupply unit 110, and the CO₂ removing unit 131 may cool the exhaust gas,from which the SO_(x) is removed, through reaction with the seawatersupplied from the seawater supply unit 110, react the cooled exhaust gaswith the absorbent liquid supplied from the absorbent liquid producingunit 120 to convert CO₂ into an aqueous ammonium salt solution, andabsorb and remove CO₂.

Specifically, the SO_(x) absorbing unit 132 is a section that is inprimary contact with seawater. As illustrated in FIGS. 3 and 6 , theSO_(x) absorbing unit 132 may include: a multi-stage seawater spraynozzle 132 a that dissolves SO_(x) by spraying the seawater suppliedfrom the seawater supply unit 110 downward and removes dusts such assoot; and a partition wall-shaped exhaust gas inlet pipe 132 b thatprevents cleaning water from flowing back, or an umbrella-shapedblocking plate 132 c that covers the exhaust gas inlet pipe 132 b.

On the other hand, the SO_(x) absorbing unit 132 may cool thetemperature of the exhaust gas to 27° C. to 33° C., preferably about 30°C., which is required by the CO₂ removing unit 131, through the seawaterspray nozzle 132 a or a separate cooling jacket (not illustrated). Asillustrated in FIG. 6A, porous upper plates 132 d having a passagethrough which the exhaust gas passes may be respectively formed inmulti-stages under the seawater spray nozzle 132 a, so that the seawaterand the exhaust gas come into smooth contact with each other. Asillustrated in FIG. 6B, an absorption apparatus 132 e filled with apacking material for allowing the seawater and the exhaust gas to comeinto contact with each other may be formed under the seawater spraynozzle 132 a, so that the seawater dissolves SO_(x).

On the other hand, a closed loop system may be applied to add a compoundforming alkali ions, for example, a basic chemical of NaOH or MgO, tothe seawater supplied to the SO_(x) absorbing unit 132 in order tofurther increase the solubility of SO_(x).

For reference, the closed loop system involves additional consumption ofbasic chemicals, but has an advantage that the amount of circulatingseawater is small, and the open loop system that discharges SO_(x)dissolved by spraying only seawater to the outside of the vessel has noadditional consumption of basic chemicals and is simple. In order tomaximize these advantages, a hybrid system in which the open loop systemand the closed loop system are combined may be applied.

In this regard, by removing SO_(x) through the SO_(x) absorbing unit 132and then removing CO₂ through the CO₂ removing unit 131, it is possibleto solve the problem that it is difficult to remove CO₂ until SO_(x) iscompletely dissolved because the solubility of SO_(x) is high and thusSO_(x) is first changed to a compound such as NaSO₃, thereby improvingthe solubility of CO₂ and the removal efficiency of CO₂.

Here, cleaning water drained to a discharge unit 170 after SO_(x) isabsorbed by the SO_(x) absorbing unit 132 contains SO₃ ⁻, SO₄ ²⁻, soot,NaSO₃, Na₂SO₄, MgCO₃, MgSO₄, and other ionic compounds together.

On the other hand, as described above, the absorption tower 130 mayfurther include a NO_(x) absorbing unit 133 that absorbs and removesNO_(x) from the exhaust gas discharged from the vessel engine 10. Theabsorption tower 130 may cool the exhaust gas, from which the NO_(x) hasbeen removed, through reaction with the seawater supplied from theseawater supply unit 110 and may remove CO₂ by reacting the cooledexhaust gas with the absorbent liquid supplied from the absorbent liquidproducing unit 120 to convert CO₂ into an aqueous ammonium saltsolution.

That is, in the absorption tower 130, the NO_(x) absorbing unit 133 thatabsorbs and removes NO_(x) from the exhaust gas discharged from thevessel engine 10, the SO_(x) absorbing unit 132 that dissolves andremoves SO_(x) while cooling the exhaust gas, from which the NO_(x) hasbeen removed, through reaction with the seawater, and the CO₂ removingunit 131 that removes CO₂ by reacting the exhaust gas, from which theSO_(x) has been removed, with the ammonia water supplied from theabsorbent liquid producing unit 120 to convert CO₂ into NH₄HCO₃(aq) arestacked to sequentially absorb and remove the NO_(x), the SO_(x), andthe CO₂.

Therefore, since the CO₂ removing unit 131 removes NO_(x) and SO_(x) byreacting the ammonia water with the exhaust gas from which the NO_(x)and the SO_(x) have been removed, side reactions caused by NO_(x) andSO_(x) do not occur during the CO₂ removal process, thereby minimizingthe generation of impurities and obtaining NH₄HCO₃ with less impuritiesin a subsequent process.

Here, the absorption tower 130 may include the CO₂ removing unit 131,the SO_(x) absorbing unit 132, the NO_(x) absorbing unit 133, and anexhaust gas economizer (EGE) 134 to be described later, may bemodularized and combined with individual modules, and may be integratedin a single tower form, and the absorption tower 130 itself may includea single tower or a group of a plurality of towers.

Specifically, the NO_(x) absorbing unit 133 is a selective catalystreactor (SCR). As illustrated in FIG. 5 , the NO_(x) absorbing unit 133may directly supply NH₃ from the absorbent liquid recycling unit 140 toa first NH₃ spray nozzle 133 b through a blower 133 a or a compressor,or when NH₃ is insufficient, may receive urea water of a urea waterstorage tank 133 c from a second NH₃ spray nozzle 133 e through a ureawater supply pump 133 d so as to compensate for the lack of NH₃.

On the other hand, since NH₃ and CO₂ are generated when the urea wateris decomposed, it may be preferable that NH₃ is directly supplied toreduce the amount of CO₂ generated.

In addition, the absorption tower 130 may further include an EGE 134that is formed between the NO_(x) absorbing unit 133 and the SO_(x)absorbing unit 132 and performs heat exchange between waste heat of thevessel engine 10 and boiler water.

Next, the absorbent liquid recycling unit 140 may recycle NH₃ from theaqueous ammonium salt solution and return NH₃ back to the CO₂ removingunit 131 of the absorption tower 130 through the absorbent liquidcirculating unit 150 for reuse as a CO₂ absorbent liquid, may store CO₂in the form of CaCO₃(s) or MgCO₃(s) or discharge CO₂ to the outside ofthe vessel, or may supply NH₃ to the NO_(x) absorbing unit 133 so as toabsorb NO_(x).

Specifically, as illustrated in FIG. 4 , the absorbent liquid recyclingunit 140 may include: a storage tank 141 that stores an aqueous divalentmetal hydroxide solution; a mixing tank 142 in which the aqueousdivalent metal hydroxide solution and the aqueous ammonium salt solutiondischarged from the absorption tower 130 are stirred by an agitator togenerate NH₃(g) and carbonate as shown in [Chemical Formula 3] below;and a filter 143 that suctions a solution and precipitate from themixing tank 142 and separates the carbonate.

NH₄HCO₃+Ca(OH)₂<->CaCO₃(s)+2H₂O+NH₃(g)

NH₄HCO₃+Mg(OH)₂<->MgCO₃(s)+2H₂O+NH₃(g)   [Chemical Formula 3]

In addition, the aqueous divalent metal hydroxide solution stored in thestorage tank 141 may be Ca(OH)₂ or Mg(OH)₂ produced by reacting thefresh water with CaO or MgO.

For example, when the concentration of the ammonia water circulatingthrough the absorbent liquid circulation line A is low, the amount of(NH₄)₂CO₃ produced in [Chemical Formula 2] decreases, resulting in anincrease in the amount of CO₂ emitted. When the concentration of theammonia water is high, the amount of carbonate produced increases morethan necessary due to excessive CO₂ absorption. Thus, it is necessary toconstantly maintain the concentration of the ammonia water so that theCO₂ absorption performance of the absorption tower 130 is kept. In orderto achieve this purpose, the concentration of the ammonia water may bedesigned to be adjusted to 12% by mass, but the present invention is notlimited thereto and the concentration of the ammonia water may bechanged according to the conditions of use.

In addition, a separate storage tank (not illustrated) that storescarbonate (CaCO₃(s) or MgCO₃(s)) separated by the filter 143 in a slurrystate or a solid state transferred to a dryer (not illustrated) andsolidified may be provided, and carbonate (CaCO₃(s) or MgCO₃(s)) may bedischarged to the outside of the vessel without being stored. Here, asan example of the filter 143, a membrane filter suitable for precipitateseparation by high-pressure fluid transfer may be applied.

On the other hand, the fresh water or the ammonia water separated by thefilter 143 is supplied to the absorbent liquid circulating unit 150, orsurplus fresh water additionally generated by the mixing tank 142relative to the total circulating fresh water is stored in a fresh watertank (not illustrated) and reused when the aqueous divalent metalhydroxide solution is generated in the storage tank 141, thereby savingthe fresh water.

In this manner, since only the relatively inexpensive metal oxide (CaOor MgO) or aqueous divalent metal hydroxide solution (Ca(OH)₂ orMg(OH)₂) is added, no additional addition of water is required, there isno decrease in the concentration of ammonia water, the capacity size ofthe filter 143 may be reduced, and the NH₃ recycling cost may bereduced. That is, in theory, only the metal oxide is consumed and NH₃and fresh water are reused, thereby significantly reducing the CO₂removal cost.

In addition, ammonia gas generated in the mixing tank 142 may besupplied to the CO₂ removing unit 131 of the absorption tower 130, ormay be supplied to the NO_(x) absorbing unit 133.

Next, in order to maximize the absorption of CO₂ by continuouslycirculating the absorbent liquid to the absorption tower 130, theabsorbent liquid circulating unit 150 circulates the high-concentrationaqueous ammonium salt solution discharged from the CO₂ removing unit 131of the absorption tower 130 and a part of the absorbent liquid that hasnot reacted with CO₂ to the ammonia water spray nozzle 131 a of the CO₂removing unit 131, so that only a part of the aqueous ammonium saltsolution is converted into carbonate by the absorbent liquid recyclingunit 140, and maintains the CO₂ absorption rate by circulating theremaining unreacted absorbent liquid to the absorption tower 130.

Specifically, as illustrated in FIG. 4 , the absorbent liquidcirculating unit 150 may include: a centrifugal pump-type ammonia watercirculation pump 151 that circulates the aqueous ammonium salt solutionand a part of the unreacted absorbent liquid through the absorbentliquid circulation line A; and a pH sensor 152 that measures theconcentration of the absorbent liquid supplied to the upper end of theCO₂ removing unit 131.

Here, when the concentration of HCO₃ ⁻ in the absorbent liquid is high,the amount of CO₂ absorbed decreases, resulting in an increase in theamount of CO₂ emitted. When the concentration of HCO₃ ⁻ is low, theamount of carbonate produced increases more than necessary due toexcessive CO₂ absorption. Therefore, by continuously monitoring theconcentration of the absorbent liquid through the pH sensor 152, theconcentration of HCO⁻ or OH⁻ in the absorbent liquid, that is, pH, maybe maintained at an appropriate level.

In this manner, a part of the aqueous ammonium salt solution flowingthrough the absorbent liquid circulation line A may be transferred tothe mixing tank 142 of the absorbent liquid recycling unit 140 andconverted into carbonate so that only a part of CO₂ is removed. Bysupplying the ammonia water recycled by the filter 143 to the absorbentliquid circulation line A, the absorbent liquid having a highconcentration of OH⁻ and a low concentration of HCO₃ ⁻ may be suppliedto maintain the CO₂ absorption rate.

Therefore, since CO₂ absorbed by taking only a part of the absorbentliquid used when collecting CO₂ is removed, the device sizes of theabsorbent liquid recycling unit 140 and the absorbent liquid circulatingunit 150 may be kept small, continuous operation may be enabled, and itis possible to flexibly cope with the CO₂ absorption rate according tothe load change of the vessel engine 10.

Next, as illustrated in FIG. 7 , the steam generating unit 160 mayinclude: an auxiliary boiler 161 that receives a mixture in the form ofsaturated water and steam heat-exchanged through the EGE 134, separatesthe steam by a steam drum (not illustrated), and supplies the separatedsteam to a steam consumer; a boiler water circulation pump 162 thatcirculates and supplies boiler water from the auxiliary boiler 161 tothe EGE 134; a cascade tank 163 that recovers condensed water condensedand phase-changed after being consumed from the steam consumer; and asupply pump 164 and a control valve 165 that supply boiler water fromthe cascade tank 163 to the auxiliary boiler 161 while controlling theamount of boiler water. The steam generating unit 160 generates andsupplies steam required for heating devices in the vessel.

Here, when the load of the vessel engine 10 is large, the amount of heatthat may be provided from the exhaust gas is large, and thus the amountof steam required in the vessel may be sufficiently produced through theEGE 134; otherwise, the auxiliary boiler 161 itself may burn fuel toproduce necessary steam.

Next, as illustrated in FIG. 7 , the discharge unit 170 may include: acleaning water tank 171 that stores cleaning water discharged from theabsorption tower 130; a water treatment device 173 including a filteringunit that controls turbidity to satisfy the outboard discharge conditionof the cleaning water transferred from the cleaning water tank 171 bythe transfer pump 172, and a neutralizing agent injecting unit thatcontrols pH; and a sludge storage tank 174 that separates and storessolid emissions such as soot. The discharge unit 170 may discharge thecleaning water, which passes through the water treatment device 173 andsatisfies the outboard discharge condition, to the outside of thevessel, and may separately store the solid emissions, such as soot,which do not satisfy the outboard discharge conditions, in the sludgestorage tank 174.

On the other hand, NaOH may be used as the neutralizing agent forsatisfying the outboard discharge condition. However, assuming that thematerials discharged from the absorption tower 130 are acidic and basic,a neutralizing agent capable of neutralizing each of the acidic materialand the basic material may be selected and used as necessary.

On the other hand, according to another embodiment of the presentinvention, a vessel including the apparatus for reducing greenhouse gasemission may be provided.

Therefore, the apparatus for reducing greenhouse gas emission in thevessel has the following effects. Since CO₂ absorbed by taking only apart of the absorbent liquid used when collecting CO₂ is removed, thedevice sizes of the absorbent liquid recycling unit 140 and theabsorbent liquid circulating unit 150 may be kept small, continuousoperation may be enabled, and it is possible to flexibly cope with theCO₂ absorption rate according to the load change of the vessel engine10. The high-concentration absorbent liquid may be supplied to preventthe decrease in greenhouse gas absorption performance. A pressurizationsystem may be applied to prevent the loss of absorbent liquid due to thenatural evaporation of high-concentration absorbent liquid. In order tosatisfy the IMO greenhouse gas emission regulations, greenhouse gas maybe converted into materials that do not affect environments and thenseparately discharged or may be converted into useful materials and thenstored. NH₃ may be recycled to minimize consumption of relativelyexpensive NH₃. The capacity size of the rear end of a filter may bereduced. Side reactions caused by SO_(x) remaining during NH₃ recyclingmay be removed, thereby minimizing the loss of NH₃ and preventingimpurities from being included when recovering ammonia.

Referring to FIG. 10 , an apparatus for reducing greenhouse gas emissionin a vessel according to still another embodiment of the presentinvention may include: an exhaust gas cooling unit 110′ that coolsexhaust gas discharged from a vessel engine 10′; an absorbent liquidproducing unit 120′ that produces and supplies a high-concentration CO₂absorbent liquid; an absorption tower 130′ including a CO₂ removing unit131′ that removes CO₂ by reacting the exhaust gas cooled by the exhaustgas cooling unit 110′ with the absorbent liquid supplied from theabsorbent liquid producing unit 120′ to convert CO₂ into an aqueousammonium salt solution; an absorbent liquid recycling unit 140′ thatrecycles the absorbent liquid and NH₃ by reacting the aqueous ammoniumsalt solution discharged from the absorption tower 130′ with an aqueousdivalent metal hydroxide solution, and circulates and supplies theabsorbent liquid and NH₃ to the absorption tower 130′ for reuse as theabsorbent liquid; and an absorbent liquid circulating unit 150′ thatcirculates the aqueous ammonium salt solution or a part of the unreactedabsorbent liquid discharged from the lower end of the absorption tower130′ through an absorbent liquid circulation line L to the upper end ofthe absorption tower 130′. Therefore, the high-temperature andhigh-pressure exhaust gas is cooled by a heat exchange method, therebypreventing the decrease in the concentration of the absorbent liquid,and only a part of the aqueous ammonium salt solution is converted intocarbonate and the remaining unreacted absorbent liquid is circulated tothe absorption tower 130′, thereby maintaining a CO₂ absorption rate.

Here, according to the type and specification of the vessel engine 10′(low-pressure engine or high-pressure engine) used in a main engine orpower generation engine and the type of fuel supplied to the vesselengine 10′ (HFO, MDO, LNG, MGO, LSMGO, ammonia, etc.), the absorptiontower may optionally include, in addition to the CO₂ removing unit, aNO_(x) absorbing unit or a SO_(x) absorbing unit, or may include boththe NO_(x) absorbing unit and the SO_(x) absorbing unit. In particular,when LNG is used as the fuel of the vessel engine 10′, SO_(x) is notgenerated, and thus a separate SO_(x) absorbing unit need not beinstalled. However, when LSMGO is used, a small amount of SO_(x) may begenerated, and thus a SO_(x) absorbing unit capable of simultaneouslyperforming cooling of exhaust gas and absorption by dissolution ofSO_(x) may be additionally provided.

Hereinafter, an embodiment in which, when LNG or LSMGO is used as thefuel of the vessel engine 10′, the NO_(x) absorbing unit, the exhaustgas cooling unit, and the CO₂ removing unit are sequentially stacked onthe absorption tower will be described, but the present invention is notlimited thereto. As described above, the NO_(x) absorbing unit and/orthe SO_(x) absorbing unit may or may not be included according to thetypes of vessel engine and fuel.

Hereinafter, the apparatus for reducing greenhouse gas emission in thevessel will be described in detail with reference to FIGS. 10 to 16 .

First, the exhaust gas cooling unit 110′ cools exhaust gas dischargedfrom the vessel engine 10′ so that temperature of the exhaust gas islowered to facilitate absorption of CO₂ by a greenhouse gas absorbentliquid.

For example, as illustrated in FIG. 12 , the exhaust gas cooling unit110′ may cool the exhaust gas discharged from the vessel engine 10′ by aheat exchange method of the fresh water. Specifically, thehigh-temperature and high-pressure exhaust gas may be cooled by the heatexchange with the fresh water to a temperature of 27° C. to 33° C.,which is required by the CO₂ removing unit 131′, by circulating thefresh water supplied from an onboard cooling system 20′ to a heatexchange pipe 111′ surrounding an exhaust gas discharge pipe 11′ throughwhich the exhaust gas flows.

That is, in a water cooling method in which the exhaust gas is directlycooled by the fresh water, the concentration of the absorbent liquid islowered due to the addition of the fresh water, resulting in adeterioration in the greenhouse gas absorption performance. By improvingthe water cooling method, the high-temperature and high-pressure exhaustgas is cooled by a heat exchange method without direct contact with thefresh water, thereby preventing the decrease in the concentration of theabsorbent liquid and preventing the deterioration in greenhouse gasabsorption performance.

On the other hand, an example in which the exhaust gas cooling unit 110′performs cooling by the heat exchange method using the fresh water hasbeen described, but various cooling media and cooling methods may beapplied.

Next, in order to supply the high-concentration absorbent liquid formaintaining the concentration of the absorbent liquid circulatingthrough the absorbent liquid circulation line L, the absorbent liquidproducing unit 120′ reacts fresh water with NH₃ as shown in [ChemicalFormula 4] below to produce high-concentration ammonia water(NH₄OH(aq)), which is a high-concentration CO₂ absorbent liquid, andsupplies the high-concentration ammonia water (NH₄OH(aq)) through theabsorbent liquid circulating unit 150′ to the CO₂ removing unit 131′formed at the upper end of the absorption tower 130′.

NH₃+H₂O->NH₄OH(aq), (exothermic reaction, 1650 MJ/ton)   [ChemicalFormula 4]

Specifically, as illustrated in FIGS. 11 and 13 , the absorbent liquidproducing unit 120′ may include: a fresh water tank (not illustrated)that stores fresh water; a fresh water control valve 121′ that suppliesthe fresh water from the fresh water tank to an ammonia water tank 123′;a NH₃ storage 122′ that stores high-pressure NH₃; an ammonia water tank123′ that produces and stores high-concentration ammonia water byspraying NH₃ supplied from the NH₃ storage 122′ to the fresh watersupplied by the fresh water control valve 121′; a pH sensor 124′ thatmeasures the concentration of the ammonia water in the ammonia watertank 123′; and an ammonia water supply pump 125′ that supplies thehigh-concentration ammonia water from the ammonia water tank 123′ to theabsorbent liquid circulation line L of the absorbent liquid circulatingunit 150′.

The concentration of the ammonia water that is the absorbent liquidcirculating through the absorption tower 130′ and the absorbent liquidrecycling unit 140′ along the absorbent liquid circulation line Lchanges as the operation is repeated. For example, the concentration ofthe ammonia water is reduced when NH₃ is supplied to the NO_(x)absorbing unit 132′ and used to absorb and remove NO_(x), or when NH₃passes through the absorption tower 130′ and is exhausted to theatmosphere together with the exhaust gas. When the concentration of theammonia water is reduced, the absorbent liquid producing unit 120′supplies the high-concentration ammonia water to the absorbent liquidcirculation line L of the absorbent liquid circulating unit 150′ tocompensate for the reduced concentration of the ammonia water so thatthe ammonia water is constantly maintained at a concentration designedas the absorbent liquid.

That is, the absorbent liquid producing unit 120′ compensates for thereduced concentration of the ammonia water by supplying the ammoniawater to the CO₂ removing unit 131′ during initial operation of theabsorption tower 130′, and replenishing the high-concentration ammoniawater to the absorbent liquid circulation line L when the concentrationof the ammonia water decreases during repeated operations of theabsorption tower 130′.

On the other hand, since the high-concentration ammonia water has ahigher partial pressure of NH₃(g) than that of the low-concentrationammonia water at the same temperature, NH₃ is relatively more evaporatedin an atmospheric pressure state, resulting in an increase in loss.Therefore, in order to store the high-concentration ammonia water, it isnecessary to lower temperature in order for increasing the solubility ofNH₃(g) and reducing the vapor pressure of NH₃(g) and to operate under apressurization system.

That is, in order to prevent a phenomenon that NH₃(g) is evaporated andlost, compressed air of a certain pressure may be injected into theupper portion of the ammonia water in the ammonia water tank 123′ sothat the pressure in the ammonia water tank 123′ is maintained to behigh, thereby constantly maintaining the concentration of the ammoniawater with NH₃ of a high concentration, for example, 50% wt.

For example, since NH₃ may be stored in a liquid state at −34° C. and8.5 bar, 50% concentration of ammonia water may be stored in the ammoniawater tank 123′ by maintaining the inside of the ammonia water tank 123′at a constant pressure by using compressed air of 7 bar available in thevessel.

In addition, a safety valve 123 a′ for reducing the pressure byexhausting air to a safety area so as to prevent overpressure of theammonia water tank 123′ may be installed.

Next, the absorption tower 130′ includes a CO₂ removing unit 131′ thatremoves CO₂ by reacting the exhaust gas cooled by the exhaust gascooling unit 110′ with the ammonia water supplied from the absorbentliquid producing unit 120′ or the ammonia water circulating along theabsorbent liquid circulation line L to convert CO₂ into an aqueousammonium salt solution as shown in [Chemical Formula 5] below.

2NH₄OH+CO₂->(NH₄)₂CO₃+H₂O

(NH₄)₂CO₃+CO₂+H₂O->2NH₄HCO₃   [Chemical Formula 5]

Specifically, as illustrated in FIG. 12 , the CO₂ removing unit 131′ mayinclude: an ammonia water spray nozzle 131 a′ that sprays the ammoniawater supplied from the absorbent liquid circulating unit 150′ downwardtoward a packing material 131 b′; the packing material 131 b′ thatcontacts CO₂ of the exhaust gas with the ammonia water to convert CO₂into NH₄HCO₃(aq); a cooling jacket (not illustrated) that is formed inmulti-stages for each section of an absorption apparatus filled with thepacking material 131 b′ and cools heat generated by a CO₂ absorptionreaction; a water spray 131 c that collects NH₃ discharged to theatmosphere without reacting with CO₂; a mist removal plate 131 d′ thatis formed in a curved multi-plate shape and returns the ammonia waterscattered when sprayed by the ammonia water spray nozzle 131 a′ towardthe packing material 131 b′; a partition wall 131 e′ that is formed sothat the ammonia water passing through the packing material 131 b′ doesnot leak out and flow back to the NO_(x) absorbing unit 132′; and anumbrella-shaped blocking plate 131 f′ that covers an upper end of anexhaust gas inlet hole surrounded by the partition wall 131 e′.

Here, the cooling jacket may cool heat to 30° C. to 50° C. at which thematerial shear is smoothest, so that NH₃ is not evaporated and lostwhile maintaining a CO₂ absorption rate at a certain level.

On the other hand, the CO₂ removing unit 131′ may be considered invarious forms so as to operate within an allowable pressure drop of anexhaust pipe required by an engine specification while increasing acontact area between the exhaust gas and NH₃. For example, the packingmaterial 131 b′ may include multi-stage distilling column packingsdesigned to increase a contact area per unit volume. As illustrated inFIG. 15 , a distilling column packing suitable for an absorption processmay be selected considering the contact area per unit area, the pressuredrop of gas, and the flooding velocity. As illustrated in FIG. 16 , theammonia water spray nozzle 131 a′ may be provided in a ladder pipe formFIG. 16A or a spray form FIG. 16B.

In addition, a solution redistributor (not illustrated) may be formedbetween the distilling column packings so as to prevent channeling whenthe ammonia water passes downward through the packing material 131 b′,the exhaust gas passes upward through the packing material 131 b′, andthe ammonia water and the exhaust gas contact each other.

In addition, the mist removal plate 131 d′ allows the scattered ammoniawater to adhere to the curved multi-plate, so that droplets becomelarge, and drains the ammonia water toward the packing material 131 b′by the own weight thereof.

On the other hand, as described above, the vessel engine 10′ is based onthe premise of using LNG or LSMGO as fuel. When the vessel engine 10′uses LNG as fuel, SO_(x) may not be generated, but when the vesselengine 10′ uses LSMGO as fuel, SO_(x) may be included in the exhaustgas, and thus the absorption tower 130′ may include the SO_(x) absorbingunit.

For example, although not separately illustrated, the SO_(x) absorbingunit may dissolve and remove SO_(x) while cooling the exhaust gasdischarged from the vessel engine 10′ through reaction with theseawater, and the CO₂ removing unit 131′ may absorb and remove CO₂ byreacting the cooled exhaust gas, from which the SO_(x) is removed, withthe absorbent liquid supplied from the absorbent liquid producing unit120′ to convert CO₂ into an aqueous ammonium salt solution.

In addition, as described above, the absorption tower 130′ may furtherinclude a NO_(x) absorbing unit 132′ that absorbs and removes NO_(x)from the exhaust gas discharged from the vessel engine 10′. The exhaustgas from which the NO_(x) has been removed may be cooled by the exhaustgas cooling unit 110′, and CO₂ may be removed by reacting the cooledexhaust gas with the absorbent liquid supplied from the absorbent liquidproducing unit 120′ to convert CO₂ into an aqueous ammonium saltsolution.

That is, in the absorption tower 130′, the NO_(x) absorbing unit 132′that absorbs and removes NO_(x) from the exhaust gas discharged from thevessel engine 10′, and the CO₂ removing unit 131′ that removes CO₂ byreacting the cooled exhaust gas, from which the NO_(x) has been removed,with the ammonia water supplied from the absorbent liquid producing unit120′ to convert CO₂ into NH₄HCO₃(aq) are stacked to sequentially absorband remove the NO_(x) and the CO₂ from the exhaust gas.

Therefore, since the CO₂ removing unit 131′ reacts the ammonia waterwith the exhaust gas from which the NO_(x) has been removed by theNO_(x) absorbing unit 132′, side reactions caused by NO_(x) do not occurduring the CO₂ removal process, thereby minimizing the generation ofimpurities and obtaining NH₄HCO₃(aq) with less impurities in asubsequent process.

Here, the absorption tower 130′ may include the CO₂ removing unit 131′,the NO_(x) absorbing unit 132′, and an EGE 133′ to be described later,may be modularized and combined with individual modules, and may beintegrated in a single tower form, and the absorption tower 130′ itselfmay include a single tower or a group of a plurality of towers.

Specifically, the NO_(x) absorbing unit 132′ is an SCR. As illustratedin FIG. 12 , the NO_(x) absorbing unit 132′ may absorb NO_(x) bydirectly supplying the recycled NH₃ from the absorbent liquid recyclingunit 140′ to a NH₃ spray nozzle 132 b′ through a blower 132 a′ or acompressor, or when NH₃ supplied to the NH₃ spray nozzle 132 b′ isinsufficient, may receive urea water of a urea water storage tank 132 cfrom a NH₃ spray nozzle 132 e′ through a urea water supply pump 132 d′so as to compensate for the loss or lack of NH₃.

On the other hand, since NH₃ and CO₂ are generated when the urea wateris decomposed, it may be preferable that NH₃ is directly supplied toreduce the amount of CO₂ generated.

In addition, the absorption tower 130′ may further include an EGE 133′that is formed between the NO_(x) absorbing unit 132′ and the exhaustgas cooling unit 110′ and performs heat exchange between waste heat ofthe vessel engine 10′ and boiler water.

Next, the absorbent liquid recycling unit 140′ may recycle NH₃ from theaqueous ammonium salt solution and return NH₃ back to the CO₂ removingunit 131′ of the absorption tower 130′ through the absorbent liquidcirculating unit 150′ for reuse as a CO₂ absorbent liquid, may store CO₂in the form of CaCO₃(s) or MgCO₃(s) or discharge CO₂ to the outside ofthe vessel, or may supply NH₃ to the NO_(x) absorbing unit 132′ so as toabsorb NO_(x).

Specifically, as illustrated in FIG. 13 , the absorbent liquid recyclingunit 140′ may include: a storage tank 141′ that stores an aqueousdivalent metal hydroxide solution; a mixing tank 142′ in which theaqueous divalent metal hydroxide solution and the aqueous ammonium saltsolution discharged from the absorption tower 130′ are stirred by anagitator to generate NH₃(g) and carbonate as shown in [Chemical Formula6] below; and a filter 143′ that suctions a solution and precipitatefrom the mixing tank 142′ and separates carbonate.

NH₄HCO₃+Ca(OH)₂<->CaCO₃(s)+2H₂O+NH₃(g)

NH₄HCO₃+Mg(OH)₂<->MgCO₃(s)+2H₂O+NH₃(g)   [Chemical Formula 6]

In addition, the aqueous divalent metal hydroxide solution stored in thestorage tank 141′ may be Ca(OH)₂ or Mg(OH)₂ produced by reacting thefresh water with CaO or MgO.

For example, when the concentration of the ammonia water circulatingthrough the absorbent liquid circulation line L is low, the amount of(NH₄)₂CO₃ produced in [Chemical Formula 5] decreases, resulting in anincrease in the amount of CO₂ emitted. When the concentration of theammonia water is high, the amount of carbonate produced increases morethan necessary due to excessive CO₂ absorption. Thus, it is necessary toconstantly maintain the concentration of the ammonia water so that theCO₂ absorption performance of the absorption tower 130′ is kept. Inorder to achieve this purpose, the concentration of the ammonia watermay be designed to be adjusted to 12% by mass, but the present inventionis not limited thereto and the concentration of the ammonia water may bechanged according to the conditions of use.

In addition, a separate storage tank (not illustrated) that storescarbonate (CaCO₃(s) or MgCO₃(s)) separated by the filter 143′ in aslurry state or a solid state transferred to a dryer (not illustrated)and solidified may be provided, and carbonate (CaCO₃(s) or MgCO₃(s)) maybe directly discharged to the outside of the vessel without beingstored. Here, as an example of the filter 143′, a membrane filtersuitable for precipitate separation by high-pressure fluid transfer maybe applied.

On the other hand, the fresh water or the ammonia water separated by thefilter 143′ is supplied to the absorbent liquid circulating unit 150′,or surplus fresh water additionally generated by the mixing tank 142′relative to the total circulating fresh water is stored in a fresh watertank (not illustrated) and reused when the aqueous divalent metalhydroxide solution is generated in the storage tank 141′, thereby savingthe fresh water.

In this manner, since only the relatively inexpensive metal oxide (CaOor MgO) or aqueous divalent metal hydroxide solution (Ca(OH)₂ orMg(OH)₂) is added, no additional addition of water is required, there isno decrease in the concentration of ammonia water, the capacity size ofthe filter 143′ may be reduced, and the NH₃ recycling cost may bereduced. That is, in theory, only the metal oxide is consumed and NH₃and fresh water are reused, thereby significantly reducing the CO₂removal cost.

In addition, ammonia gas generated in the mixing tank 142′ may besupplied to the CO₂ removing unit 131′ of the absorption tower 130′, ormay be supplied to the NO_(x) absorbing unit 132′.

Next, in order to maximize the absorption of CO₂ by continuouslycirculating the absorbent liquid to the absorption tower 130′, theabsorbent liquid circulating unit 150′ circulates the high-concentrationaqueous ammonium salt solution discharged from the CO₂ removing unit131′ of the absorption tower 130′ and a part of the absorbent liquidthat has not reacted with CO₂ to the ammonia water spray nozzle 131 a′of the CO₂ removing unit 131′, so that only a part of the aqueousammonium salt solution is converted into carbonate by the absorbentliquid recycling unit 140′, and maintains the CO₂ absorption rate bycirculating the remaining unreacted absorbent liquid to the absorptiontower 130′.

Specifically, as illustrated in FIGS. 10 and 13 , the absorbent liquidcirculating unit 150′ may include: a centrifugal pump-type ammonia watercirculation pump 151′ that circulates the high-concentration aqueousammonium salt solution and a part of the unreacted absorbent liquidthrough the absorbent liquid circulation line L; and a pH sensor 152′that measures the concentration of the absorbent liquid supplied to theupper end of the CO₂ removing unit 131′.

Here, when the concentration of HCO₃ ⁻ in the absorbent liquid is high,the amount of CO₂ absorbed decreases, resulting in an increase in theamount of CO₂ emitted. When the concentration of HCO₃ ⁻ is low, theamount of carbonate produced increases more than necessary due toexcessive CO₂ absorption. Therefore, by continuously monitoring theconcentration of the absorbent liquid through the pH sensor 152′, theconcentration of HCO₃ ⁻ or OH⁻ in the absorbent liquid, that is, pH, maybe maintained at an appropriate level.

In this manner, a part of the aqueous ammonium salt solution flowingthrough the absorbent liquid circulation line L may be transferred tothe mixing tank 142′ of the absorbent liquid recycling unit 140′ andconverted into carbonate so that only a part of CO₂ is removed. Bysupplying the ammonia water recycled by the filter 143′ to the absorbentliquid circulation line L, the absorbent liquid having a highconcentration of OH⁻ and a low concentration of HCO₃ ⁻ may be suppliedto maintain the CO₂ absorption rate.

Therefore, since CO₂ absorbed by taking only a part of the absorbentliquid used when collecting CO₂ is removed, the device sizes of theabsorbent liquid recycling unit 140′ and the absorbent liquidcirculating unit 150′ may be kept small, continuous operation may beenabled, and it is possible to flexibly cope with the CO₂ absorptionrate according to the load change of the vessel engine 10′.

Next, as illustrated in FIG. 14 , the steam generating unit 160′ mayinclude: an auxiliary boiler 161′ that receives a mixture in the form ofsaturated water and steam heat-exchanged with exhaust gas through theEGE 133′, separates the steam by a steam drum (not illustrated), andsupplies the separated steam to a steam consumer; a boiler watercirculation pump 162′ that circulates and supplies boiler water from theauxiliary boiler 161′ to the EGE 133′; a cascade tank 163′ that recoverscondensed water condensed and phase-changed after being consumed fromthe steam consumer; and a supply pump 164′ and a control valve 165′ thatsupply boiler water from the cascade tank 163′ to the auxiliary boiler161′ while controlling the amount of boiler water. The steam generatingunit 160′ generates and supplies steam required for heating devices inthe vessel.

Here, when the load of the vessel engine 10′ is large, the amount ofheat that may be provided from the exhaust gas is large, and thus theamount of steam required in the vessel may be sufficiently producedthrough the EGE 133′; otherwise, the auxiliary boiler 161′ itself mayburn fuel to produce necessary steam.

On the other hand, according to still another embodiment of the presentinvention, a vessel including the apparatus for reducing greenhouse gasemission may be provided.

Therefore, the apparatus for reducing greenhouse gas emission in thevessel and the vessel including the same have the following effects. Thehigh-temperature and high-pressure exhaust gas may be cooled by the heatexchange method, thereby preventing the decrease in the concentration ofthe absorbent liquid. Since CO₂ absorbed by taking only a part of theabsorbent liquid used when collecting CO₂ is removed, the device sizesof the absorbent liquid recycling unit and the absorbent liquidcirculating unit may be kept small, continuous operation may be enabled,and the recovery rate of the absorbent liquid may be increased, therebypreventing the deterioration in the greenhouse gas absorptionperformance. It is possible to flexibly cope with the CO₂ absorptionrate according to the load change of the vessel engine. A pressurizationsystem may be applied to prevent the loss of absorbent liquid due to thenatural evaporation of NH₃ of high-concentration absorbent liquid. Inorder to satisfy the IMO greenhouse gas emission regulations, greenhousegas may be converted into materials that do not affect environments andthen separately discharged or may be converted into useful materials andthen stored. NH₃ may be recycled to minimize consumption of relativelyexpensive NH₃. The capacity size of the rear end of a filter may bereduced. Greenhouse gases may be stored in the form of carbonates thatexist in the natural state, and may be discharged to the sea. Sidereactions caused by NO_(x) or SO_(x) remaining during NH₃ recycling maybe removed, thereby minimizing the loss of NH₃ and preventing impuritiesfrom being included when recovering ammonia.

The present invention has been described above with reference to theembodiments illustrated in the drawings. However, the present inventionis not limited thereto, and various modifications or other embodimentsfalling within the scope equivalent to the present invention can be madeby those of ordinary skill in the art. Therefore, the true scope ofprotection of the present invention should be determined by the appendedclaims.

1-36. (canceled)
 37. An apparatus for reducing greenhouse gas emissionin a vessel, the apparatus comprising: a seawater supply unit thatsupplies seawater; an absorbent liquid producing unit that produces andsupplies a high-concentration CO₂ absorbent liquid; an absorption towercomprising a CO₂ removing unit that cools exhaust gas discharged from avessel engine by reacting the exhaust gas with the seawater suppliedfrom the seawater supply unit, and removes CO₂ by reacting the cooledexhaust gas with the absorbent liquid supplied from the absorbent liquidproducing unit to convert CO₂ into an aqueous ammonium salt solution; anabsorbent liquid recycling unit that recycles the absorbent liquid andNH₃ by reacting the aqueous ammonium salt solution discharged from theabsorption tower with an aqueous divalent metal hydroxide solution andcirculates and supplies the absorbent liquid and the NH₃ to theabsorption tower for reuse as the absorbent liquid; and an absorbentliquid circulating unit that circulates the aqueous ammonium saltsolution or a part of an unreacted absorbent liquid discharged from alower end of the absorption tower through an absorbent liquidcirculation line to an upper end of the absorption tower.
 38. Theapparatus according to claim 37, wherein the absorbent liquidcirculating unit comprises: an ammonia water circulation pump thatcirculates the aqueous ammonium salt solution and a part of theunreacted absorbent liquid through the absorbent liquid circulationline; and a pH sensor that measures a concentration of the absorbentliquid supplied to the upper end of the absorption tower.
 39. Theapparatus according to claim 37, wherein the absorbent liquid recyclingunit comprises: a storage tank that stores the aqueous divalent metalhydroxide solution; a mixing tank in which the aqueous divalent metalhydroxide solution and the aqueous ammonium salt solution dischargedfrom the absorption tower are stirred by an agitator to generate NH₃(g)and carbonate; and a filter that suctions a solution and precipitatefrom the mixing tank and separates the carbonate.
 40. The apparatusaccording to claim 39, wherein the NH₃(g) generated by the mixing tankis supplied to the absorption tower, or the absorbent liquid separatedby the filter is supplied to the absorbent liquid circulating unit. 41.The apparatus according to claim 39, wherein fresh water or ammoniawater separated by the filter is supplied to the absorbent liquidproducing unit, or surplus fresh water additionally generated by themixing tank relative to a total circulating fresh water is stored in afresh water tank and reused when the aqueous divalent metal hydroxidesolution is generated in the storage tank.
 42. The apparatus accordingto claim 37, wherein the absorption tower further comprises a SO_(x)absorbing unit that dissolves and removes SO_(x) while cooling theexhaust gas discharged from the vessel engine by reacting the exhaustgas with the seawater supplied from the seawater supply unit, and theCO₂ removing unit cools the exhaust gas, from which the SO_(x) has beenremoved, by reacting the exhaust gas with the seawater supplied from theseawater supply unit and removes CO₂ by reacting the cooled exhaust gaswith the absorbent liquid supplied from the absorbent liquid producingunit to convert CO₂ into the aqueous ammonium salt solution.
 43. Theapparatus according to claim 37, wherein the absorption tower furthercomprises a NO_(x) absorbing unit that absorbs and removes NO_(x) fromthe exhaust gas emitted from the vessel engine, and the CO₂ removingunit cools the exhaust gas, from which the NO_(x) has been removed, byreacting the exhaust gas with the seawater supplied from the seawatersupply unit and removes CO₂ by reacting the cooled exhaust gas with theabsorbent liquid supplied from the absorbent liquid producing unit toconvert CO₂ into the aqueous ammonium salt solution.
 44. The apparatusaccording to claim 37, wherein, in the absorption tower, a NO_(x)absorbing unit that absorbs and removes NO_(x) from the exhaust gasdischarged from the vessel engine, a SO_(x) absorbing unit thatdissolves and removes SO_(x) while cooling the exhaust gas, from whichthe NO_(x) has been removed, through reaction with the seawater suppliedfrom the seawater supply unit, and the CO₂ removing unit that removesCO₂ by reacting the exhaust gas, from which the SO_(x) has been removed,with the absorbent liquid supplied from the absorbent liquid producingunit to convert CO₂ into the aqueous ammonium salt solution aresequentially stacked.
 45. The apparatus according to claim 37, whereinthe absorbent liquid producing unit comprises: a fresh water tank thatstores fresh water; a fresh water control valve that supplies the freshwater from the fresh water tank; a NH₃ storage that stores high-pressureNH₃; an ammonia water tank that produces and stores high-concentrationammonia water, which is the absorbent liquid, by spraying the NH₃supplied from the NH₃ storage to the fresh water supplied by the freshwater control valve; a pH sensor that measures a concentration of theammonia water in the ammonia water tank; and an ammonia water supplypump that supplies the ammonia water from the ammonia water tank to theabsorbent liquid circulating unit.
 46. The apparatus according to claim37, wherein the CO₂ removing unit comprises: an ammonia water spraynozzle that sprays the absorbent liquid downward; a packing materialthat contacts the CO₂ with the ammonia water, which is the absorbentliquid, to convert CO₂ into NH₄HCO₃(aq); a cooling jacket that is formedin multi-stages for each section of an absorption apparatus filled withthe packing material and cools heat generated by a CO₂ absorptionreaction; a water spray that collects NH₃ discharged to the outsidewithout reacting with CO₂; a mist removal plate that is formed in acurved multi-plate shape and returns the ammonia water toward thepacking material; a partition wall that is formed so that the ammoniawater does not flow back; and an umbrella-shaped blocking plate thatcovers an exhaust gas inlet hole surrounded by the partition wall. 47.An apparatus for reducing greenhouse gas emission in a vessel, theapparatus comprising: an exhaust gas cooling unit that cools exhaust gasdischarged from a vessel engine; an absorbent liquid producing unit thatproduces and supplies a high-concentration CO₂ absorbent liquid; anabsorption tower comprising a CO₂ removing unit that removes CO₂ byreacting the exhaust gas cooled by the exhaust gas cooling unit with theabsorbent liquid supplied from the absorbent liquid producing unit toconvert CO₂ into an aqueous ammonium salt solution; an absorbent liquidrecycling unit that recycles the absorbent liquid and NH₃ by reactingthe aqueous ammonium salt solution discharged from the absorption towerwith an aqueous divalent metal hydroxide solution and circulates andsupplies the absorbent liquid and the NH₃ to the absorption tower forreuse as the absorbent liquid; and an absorbent liquid circulating unitthat circulates the aqueous ammonium salt solution or a part of anunreacted absorbent liquid discharged from a lower end of the absorptiontower through an absorbent liquid circulation line to an upper end ofthe absorption tower.
 48. The apparatus according to claim 47, whereinthe absorbent liquid circulating unit comprises: an ammonia watercirculation pump that circulates the aqueous ammonium salt solution anda part of the unreacted absorbent liquid through the absorbent liquidcirculation line; and a pH sensor that measures a concentration of theabsorbent liquid supplied to the upper end of the absorption tower. 49.The apparatus according to claim 47, wherein the absorbent liquidrecycling unit comprises: a storage tank that stores the aqueousdivalent metal hydroxide solution; a mixing tank in which the aqueousdivalent metal hydroxide solution and the aqueous ammonium salt solutiondischarged from the absorption tower are stirred by an agitator togenerate NH₃(g) and carbonate; and a filter that suctions a solution andprecipitate from the mixing tank and separates the carbonate.
 50. Theapparatus according to claim 49, wherein the NH₃(g) generated by themixing tank is supplied to the absorption tower, or the absorbent liquidseparated by the filter is supplied to the absorbent liquid circulatingunit.
 51. The apparatus according to claim 49, wherein fresh water orammonia water separated by the filter is supplied to the absorbentliquid producing unit, or surplus fresh water additionally generated bythe mixing tank relative to a total circulating fresh water is stored ina fresh water tank and reused when the aqueous divalent metal hydroxidesolution is generated in the storage tank.
 52. The apparatus accordingto claim 47, wherein the vessel engine uses liquefied natural gas (LNG)or low sulphur marine gas oil (LSMGO) as fuel.
 53. The apparatusaccording to claim 47, wherein the exhaust gas cooling unit cools theexhaust gas to a temperature of 27° C. to 33° C. by circulating freshwater supplied from an onboard cooling system through a heat exchangepipe surrounding an exhaust gas discharge pipe.
 54. The apparatusaccording to claim 47, wherein the absorption tower further comprises aNO_(x) absorbing unit that absorbs and removes NO_(x) from the exhaustgas emitted from the vessel engine, and the CO₂ removing unit removesCO₂ by reacting the exhaust gas, from which the NO_(x) has been removedand which is cooled by the exhaust gas cooling unit, with the absorbentliquid supplied from the absorbent liquid producing unit to convert CO₂into the aqueous ammonium salt solution.
 55. The apparatus according toclaim 47, wherein the absorbent liquid producing unit comprises: a freshwater tank that stores fresh water; a fresh water control valve thatsupplies the fresh water from the fresh water tank; a NH₃ storage thatstores high-pressure NH₃; an ammonia water tank that produces and storeshigh-concentration ammonia water, which is the absorbent liquid, byspraying the NH₃ supplied from the NH₃ storage to the fresh watersupplied by the fresh water control valve; a pH sensor that measures aconcentration of the ammonia water in the ammonia water tank; and anammonia water supply pump that supplies the ammonia water from theammonia water tank to the absorbent liquid circulating unit.
 56. Theapparatus according to claim 47, wherein the CO₂ removing unitcomprises: an ammonia water spray nozzle that sprays the absorbentliquid downward; a packing material that contacts the CO₂ with theammonia water, which is the absorbent liquid, to convert the CO₂ intoNH₄HCO₃(aq); a cooling jacket that is formed in multi-stages for eachsection of an absorption apparatus filled with the packing material andcools heat generated by a CO₂ absorption reaction; a water spray thatcollects NH₃ discharged to the outside without reacting with CO₂; a mistremoval plate that is formed in a curved multi-plate shape and returnsthe ammonia water toward the packing material; a partition wall that isformed so that the ammonia water does not leak out; and anumbrella-shaped blocking plate that covers an exhaust gas inlet holesurrounded by the partition wall.